N = input()
items = [0 for i in range(11)]
for i in range(N):
	a = map(int,raw_input().split())
	for aa in a:items[aa] += 1
count = 0
for i in range(11):
	if items[i] >= 2:
		count += (items[i]/2)
		items[i] -= ((items[i]/2)*2)
print count+int(items.count(1)/4)